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2010 Rahimpour Comparative Study of Cocurrent and Countercurrent Modes of Operation for a Thermal Hydrolyzer in an Industrial Urea Wastewater Treatment Loop

In this work, a comparison of cocurrent and countercurrent modes of operation for an industrial wastewater treatment loop of an industrial urea plant has been carried out. In both modes of operation, a loop with a thermal hydrolyzer is used for urea decomposition, and two desorbers are used for the removal of ammonia and carbon dioxide. In the proposed model, the extended electrolytic UNIQUAC equation is used to describe the nonideality of the liquid phase of the NH3- CO2- H2 O- urea system, and the perturbed-hard-sphere (PHS) equation of state is applied to predict the vapor fugacity coefficients. Also, the urea hydrolysis reactors are divided into several continuously stirred tank reactors (CSTRs) and the equilibrium-stage model is applied for modeling of both kinds of reactors and of the desorbers. The simulation results show that countercurrent mode of operation is necessary to achieve new environmental standards and complete treatment. The data predicted using the model were consistent with available plant data, indicating the validity of the model. The impact of different parameters on the performance of the urea wastewater treatment loops has been examined. Overall, this study results in beneficial information about the use of the cocurrent and countercurrent hydrolysis reactors in the urea wastewater treatment process.